Various industrial processes and equipment operate at high temperature and/or pressure, and do so in environments containing corrosive fluids. In these environments, typical iron and steel equipment surfaces can be degraded by corrosive reactions with elements of the corrosive fluids, which can include, for example, carbon dioxide, hydrogen sulfide, chloride ions, and the like.
One way to avoid corrosion is to provide a protective liner that separates the corrosion-susceptible equipment surfaces from the corrosive fluids. Certification standards, such as those set by the National Association of Corrosion Engineers (NACE), typically require a bond between the protective liner and the equipment surface. Accordingly, mechanical fits fall short of these standards; however, bonding the protective liner to the equipment surfaces such that the bond is essentially free of voids, oxide films, and/or discontinuities, while still having a long corrosion-protecting life and being compliant with certification standards, may present a challenge. This challenge may be made more difficult when it is desired to create and protect generally cylindrical equipment housings for the turbomachines.
One way to affix a corrosion-resistant protective liner to a corrosion-susceptible surface is known as explosive cladding. In explosive cladding, the corrosive-resistant liner is placed on the surface to be protected of the corrosion-susceptible equipment, and then an explosion is set off proximate thereto, typically with both the liner and the equipment disposed underwater. The explosion plasticizes the surfaces of both the equipment and the liner and produces a bond therebetween. Explosive cladding, however, is typically limited in application to flat surfaces. Accordingly, if a generally cylindrical equipment housing is desired, a flat plate generally must be clad, which is subsequently rolled and welded. This additional working adds cost and time to the bonding process. Furthermore, explosive cladding requires careful planning, specialized equipment, and ballistics expertise to deal with dangerous explosive devices.
Another way to create a protective liner is to provide a weld overlay. In this process, a weld material is deposited in a layer on the equipment surface, for example, an inner surface of a nozzle body, and the process is repeated many times until a desired thickness is reached. This process, however, is time-consuming and expensive both in terms of labor and equipment. Furthermore, this process allows for potential weld defects, which, if present, may require additional reworking of the welding process, further increasing the expense and time associated with this process.
What is needed, therefore, is a process in which a corrosion-resistant protective liner is casted on an equipment surface, for example, an inner surface of a nozzle body, with the casting process generally minimizing the potential for defects in the bond between the corrosion-resistant protective liner and the equipment surface.